A range extender electric vehicle (EV) technology has been developed as one of the technologies applicable to eco-friendly vehicles such as electric vehicles. In the range extender electric vehicle technology, a first motor for an engine and a generator is mounted on the vehicle in addition to a second motor for the vehicle. Therefore, when a state of charge (SOC) of a battery falls below a threshold level, an engine output drives the first motor which is for a generator to charge the battery while the vehicle runs by the second motor (running in a series mode), thereby increasing a running distance of the vehicle.
A conventional range extender EV technology will now be briefly described with reference to FIG. 20.
Charge Depletion (CD) Mode
In a charge depletion mode in which a second motor MG2 drives a vehicle while consuming the electric power of the battery, only the second motor MG2 drives the vehicle, while the first motor MG1 for an engine and a generator does not operate.
When a required power for the second motor MG2 for driving the vehicle is, for example, set to 125 kW, the second motor MG2 for driving the vehicle produces an output of 125 kW.
Charge Sustaining (CS) Mode
When the SOC of the battery falls below a threshold level while driving using the second motor MG2, the first motor MG1 for an engine and a generator is driven by the output of the engine, and the second motor MG2 for driving the vehicle exerts an output of 20 kW while the first motor MG1 generates electric power and charges the battery. Consequently, the second motor MG2 cannot contribute to driving of the vehicle using the remaining power of about 100 kW (that is, the remaining power of about 100 kW is not employed).
As a result, in the conventional range extender EV technology, excessive power for the second motor are applied, thereby increasing manufacturing costs.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.